FR2557279A1 - INDUSTRIAL FURNACE FOR THERMAL TREATMENT OF METALLIC PARTS - Google Patents

Abstract

1 THE INVENTION CONCERNS AN INDUSTRIAL OVEN FOR HEAT TREATMENT OF METAL PARTS, INCLUDING A HEATING CHAMBER 2 CAPABLE OF RECEIVING A COOLING GAS SENT TO A LOAD 12 BY THE INTERMEDIATE OF A PIVOTING DISTRIBUTION DEVICE. 2THE PROBLEM TO BE SOLVED CONSISTS OF ENSURING A UNIFORM SCAN OF THE LOAD WITH THE COOLING GAS. 3THIS OVEN IS CHARACTERIZED IN THAT NOZZLES 21, 21 ARE PROVIDED AS A DISTRIBUTION DEVICE, THE COOLING GAS FLOWING THROUGH THESE NOZZLES BEFORE ARRIVING ON THE LOAD. 4THE INVENTION IS APPLICABLE IN PARTICULAR TO SINGLE CHAMBER VACUUM OVENS.

Description

"Industrial furnace for heat treatment of metal parts".

  The subject of the invention is an industrial oven, in particular

  a single chamber vacuum furnace for heat treatment of

  these metals, comprising a heating chamber disposed in an oven chamber and receiving a load, this chamber being heated by heating elements and having at least

  a closing chamber opening for the passage of a refractory gas

  cooling this gas can be put into circulation through a

  heat exchanger with a fan, a device

  rotating titler moved in one direction and the other during the

  cooling ratio being mounted, for the control of the flow of

  cooling gas flowing through the cooling gas line

  in the area of the chamber opening intended for entry

cooling gas.

  Industrial furnaces of this type are used in particular

  to allow the trearp of fast steel elements and other tool steels. However, they are suitable for other heat treatments, for example for white annealing. Such an oven is conopse of a double-walled steel enclosure with a front door opening to give access to the heating chamber. The heating chamber is made with an envelope

  steel coated with thermal insulation. On the bottom and on the

  the heating chamber is usually equipped with a large

  opening of gas passage. During the heating and hot keeping period, these openings are closed by isolated stop registers. The upper opening of the gas passage of the heating chamber is directly connected by a pipe of

  tubular connection to the discharge pipe of a fan.

  The flow of gas arriving in the heating chamber by

  the tubular link pipe can sweep away a load

  The increase in the load is counteracted by the reduction in the resulting cooling rate. It is also not possible to increase the fan coil discharge diameter because, if the fan power remains the same, this results in a decrease in speed. However, a high gas velocity is required to obtain rapid cooling of the charge. The execution of an operation such as

  tempering, for example, it is not possible to evacuate

  fisely fast heat. It is therefore necessary, to obtain rapid cooling of the charge, to circulate at high speed the cooling gas blown into the heating chamber. With a predetermined flow rate of the fan, the speed of the cooling gas is a function of the diameter of the tubular connection. But this is in turn decisive for

  the size of the surface of the charge swept by the gas of

  froidissement. As a result, for a constant quality of the parts undergoing the heat treatment, the production of the oven is

  necessarily limited in practice.

  In the German patent application 28 44 843, it is therefore proposed, to increase the production of the oven and for a better use of the effective power of the furnace, by subjecting to a rapid cooling a larger surface area.

  load, to pivot mount a flap on the chamber opening pre-

  view for the gas inlet, this flap controlling the flow of gas that

  arrives in the area of the free section of the chamber opening.

  Such a component scours only very imperfectly the whole of the

  charge. But, above all, the surface of the load is not uniform.

  the element is swept by the cooling gas, so that cooling is obtained which is not uniform. This results in a risk

deformation.

  The object of the invention is therefore to arrange the pivoting distributor device of an industrial furnace of the type indicated in the introduction so as to allow a uniform sweep of the

  charge with the cooling gas.

  To this end, the invention relates to an oven of the above type characterized in that nozzles are provided as a distributor, the cooling gas flowing to

  through these nozzles before arriving on the load.

  By means of the nozzles, it is possible to drive

  tionally the cooling gas on the surface of the charge so that it can be cooled uniformly. 3. Removes the risk of non-uniform sweeping of the charge surface by the cooling gas. The shape and arrangement of the nozzles can be adapted optimally to the conditions encountered. It is thus possible to obtain well-defined conditions during the cooling operation. According to an advantageous embodiment, the nozzles are mounted immediately before the chamber opening. They are thus arranged in the cold part of the oven. During the operation

  they are cooled by the cooling gas.

  flowing at high speed in the nozzle system. As a result, the amount of heat radiated by the load to the nozzle system when opening the shutoff damper closing the chamber opening causes only a slight heating. This is why it is not necessary for the nozzles to be made of special heat-resistant alloys. By this provision

  heat losses are completely excluded.

  The nozzles are preferably arranged with a shape

  cylindrical and have the same diameter.

  According to another characteristic of the invention, the pivot axis of the nozzles is arranged parallel to the section profile of the chamber opening and passing through the center of this chamber.

  profile, the nozzles being arranged parallel to the pivot axis

  following at least one line symmetrically with respect to the mediator of the sectional profile of the chamber opening, the directional actior of the nozzles thus being improved. Further optimization is achieved when the longitudinal axes of the nozzles compete at a point upstream on the mediator of the sectional profile of the chamber opening. It is thus possible to guarantee a uniform sweep of the load in the direction of pivoting

nozzles.

  In order to distribute the flow of cooling gas between the different nozzles, each nozzle is, according to another characteristic of the invention, provided with a throttling device. The throttling device and the angular arrangement of the nozzles lead to a speed. constant value scanning of jets 4.

  of gas and at a constant value arrival speed on the load.

  This ensures uniform cooling of the load

  perpendicular to the direction of pivoting.

  According to a preferred embodiment, the nozzles are arranged in the casing of a cylindrical element whose axis coincides with the axis of pivoting and whose outer lateral surface is sealingly applied when pivoting on an element of rotation. sealing arranged parallel to the cylindrical member, the sealing member being also sealingly disposed at the end of the cooling gas supply line. it

  is a simple constructive arrangement of the nozzles, this

  position operating safely.

  Since during a pivoting movement the

  nozzles blow twice on the middle of the load, which allows

  to have a faster cooling of the medium of the load, the speed of pivoting of the nozzles is preferably reduced in the

area of the end positions.

  According to another characteristic of the invention, the diameter of the nozzles is at least equal to 1/10 of the distance between the nozzles and the point of incidence on the load. This takes into account that the velocity of a gas stream exiting a nozzle decreases as one moves away from the mouth of the nozzle. The speed in the center of the jet remains at almost constant up to 10 times the diameter of the

  nozzle about. For this reason, nozzles having a di-

  relatively large meter, so that the jet arrives on the load

  with a speed substantially equal to the output speed.

  According to a preferred embodiment, it is proposed that the faces of the heating chamber opposite one to

  the other, in particular the back and the cover, be provided with

  corresponding chambers and nozzles for supplying the cooling gas into the heating chamber. As a result, the charge is subjected from two sides to the action of the cooling gas which accelerates the cooling operation and makes it even more uniform. It is then advantageous for the cooling gas supply lines to the nozzles to be equipped with throttle valves controlling the flow rate independently of one another. This is done considering that the load is placed on load supports which must also be cooled, namely in addition by the bottom nozzles. As a result, more heat must be removed at the bottom than at the top, which is possible by throttling the cooling flows by means of

  throttles in the cooling gas lines

  top and bottom. We can thus proceed to an adaptation of

  heat transfer independently of the geo-

  metric and geometric distribution of the masses of the load, ensuring uniform cooling of

causes no deformations.

  In case of too rapid cooling, it is finally possible, by means of a volumetric flow regulator arranged before the

  fan, adjust the cooling rate of the cooling gas

  sent to the nozzles and adapt this speed to the conditions encountered. An oven according to the invention is represented by

  of non-limiting example in the accompanying figures, in which

  the: - FIG. 1 is a longitudinal section of an oven

  single chamber vacuum with gas quenching device

if we;

  FIG. 2 is a cross-section taken

the line II-II of FIG. 1;

  FIG. 3 is an enlarged view of the system.

  lower nozzle section of FIG. 1; FIG. 4 is an enlarged cross-sectional view of the lower nozzle system shown in FIG. - Figs. 5a to 5g schematically represent arrangements of nozzle systems with types of construction

different ovens.

  The single chamber vacuum furnace with pressurized gas quenching device consists essentially of a 6.

  double-walled oven enclosure 1 made of steel, in which

  a furnace 2. The furnace enclosure 1 is

  and is placed on welded feet on the inside

  1. On a front side (left in Fig.1), the furnace chamber 1 is provided with a tilting front door 4 which is also made with a double wall. The opposite front side (on the right in FIG. 1) of the furnace chamber 1 has in its central part a circular opening in which is inserted a cover 5 which serves to accommodate an engine.

6 described below.

  The heating chamber 2 is made with an envelope

  pe 7 steel coated with a self-supporting graphite insulation 8.

  On the bottom and on the cover, the heating chamber 2 is provided with a large chamber opening 9, 9 'across

  which can pass the cooling gas. These openings

  room 9,9 'are, during the heating and holding period

  hot, closed by isolated stop registers 10,10 '. Soft-

  Opening and closing movement are controlled pneumatically by means of cylinders not shown. The heating chamber 2 can be mounted on wheels, not shown, for

  that it can be taken out of the oven chamber 1 in order to facilitate

the maintenance work.

  On the front side, the heating chamber 2 is closed by

  an insulated rocker 11, through which can be introduced

  in the heating chamber 2, a load 12, in the form of a load carrier, is provided. During the treatment, the charge 12 is placed on a load support 13. The interior of the heating chamber 2 can be observed through a sight, not shown,

which is arranged in the door 11.

  Inside the heating chamber 2, electric heating elements 14 are arranged above and below the charge 12. These heating elements guarantee a rapid heating of the charge 12 to the treatment temperature and high uniformity of the temperature, the supply of electric current to the heating elements 14 through the furnace enclosure 1 and 7. the envelope of the heating chamber 2 is of conventional type and does not

  will not be described here more precisely.

  Inside the furnace enclosure 1 is disposed,

  behind the heating chamber 2, a heat exchanger 15 comprising

  many cooling coils to which we send

  water through unrepresented supply lines and from

  which water can be evacuated by evacuation pipes that are not represented either. The heat exchanger 15 is used to

  ensure rapid cooling of the cooling gas

  fair on the hot parts of the load 12.

  The cooling gas is circulated by a fan 16 capable of providing a high flow rate, this fan being disposed in the furnace chamber 1, behind the heat exchanger 15 and along the same axis. The fan 16 has a

  central gas suction pipe 17 directed to the side of the sample.

  15. In this suction pipe is disposed a volumetric flow controller 18 by means of which the cooling rate can be adapted to the conditions encountered. The fan 16 is driven by the motor 6 arranged along the same axis inside the cover 5 which extends towards the rear the side

front of the oven enclosure 1.

  The fan 16 is connected with

  upper and lower cooling gas supply 19,19 '. The supply line 19 opens into the bottom and the supply line 19 'into the cover of the furnace chamber 1. In the cooling gas supply lines 19, 19' are mounted with throttle butterflies 20 , 20 'can be operated independently of one another. With these throttles, it is possible to regulate the flow of cooling gas passing through the gas lines

  19,19 'and, consequently, the supply of cooling gas

  drain on the load 12 from the top and from the bottom. We

  can thus uniformly cool loads of irregular shape.

  die. Indeed, it is possible to evacuate a larger quantity

heat of a side.

  In the zone where the cooling gas pipes 8.

  19,19 'open into the cover and into the bottom of the

  1, are arranged nozzles 21, 21 'serving as

  cooling gas distributor device. This provision

  sition is visible in particular in FIG. 3 and FIG. 4. The nozzles 21,21 'are cylindrical and have the same diameter. They are arranged online in the envelope

  22,22 'of a cylindrical element 23,23', the axis of the cylindrical element

  23,23 'inductor constituting a pivot axis 24,24'. We

  can thus rotate the cylindrical element 23,23 'conjointly

  with the nozzles 21,21 '. The pivot axis 24, 24 'is

  mounted to rotate in bearings 25, 25 'and may be

  born in rotation in one direction and the other by means of a motor not shown. The pivot axis 24, 24 'extends parallel

  to the sectional profile of the chamber opening 9, 9 'and in

  centered on this profile. The nozzles 21, 21 'are dis-

  posed symmetrically with respect to the mediator M of the section profile. The outer lateral surface 26,26 'of the cylindrical element 23,23' is applied to a sealing element 27,27 'which is also cylindrical and disposed parallel to the first element

  cylindrical. This provides a tight connection between the surface

  this outer side 26,26 'and the inner surface of the element

  27,27 'in all pivoting positions of the cylindrical member 23,23'. In the position zone

  end of the nozzles 21,21 'abut on the element of étan-

  fairness 27,27 '. The sealing element 27, 27 'surrounds in the

  sealing the mouth of the gas line

  19,19 'coldness in the cover and in the bottom of the

oven ring 1.

  The longitudinal axes L of the nozzles 21, 21 'concur

  at a point P situated upstream on the mediator M of the profile of sec-

  chamber opening 9,9 ', so that the nozzles have

  angular disposition.-They are also equipped with

  throttles 28,28 'with which one can adjust the

  distribution of the gas flow between the different nozzles. The disc

  positive throttling 28,28 'and the angular disposition of 9.

  nozzles 21, 21 'lead to an output speed of

  gas jets and at a speed of arrival of constant value.

  In this way it is possible to guarantee uniform cooling of the load 12 perpendicular to the direction of pivoting. The diameter of the nozzles 21, 21 'is equal to about 1/10 of the distance between the nozzles 21, 21' and the point of incidence on the load 12, so that the jet arrives on the load 12 with a

  a speed substantially equal to the output speed of the nozzle 21,21 '.

  Single chamber vacuum furnace with quenching device

  pressure gas described above as an example of

  tion is filled with a load 12 by the front door 4 open and the door 11 also opened by tilting. The load, arranged inside a load basket, rests on a load support 13. The door 11 of the heating chamber and the

  front door 4 are closed, for example to perform an operation

  heating ration. Similarly, the stop registers 10, 10 'of the heating chamber 2 are closed. The vacuum pump system is then activated and the heating chamber 2 is evacuated. The heating is switched on and, by means of the heating elements 14, temperatures of up to 1300 C and above are set in the heating chamber 2. Depending on the needs, we can operate

  with different temperature programs.

  After maintaining the desired working temperature for a predetermined time, the heating chamber 2 is filled, for quenching, with an inert gas under an overpressure reaching

  at most 5 bars. The fan 16 is started simultaneously

  and the 10,10 'arree registries are open. The gas of

  cooling is circulated by the fan 16 with a high flow rate and the load 12 is cooled by heat removal. An adjustment can be made by means of the volumetric flow controller 18 and throttles, 20 '. From the gas suction pipe 17, the cooling gas flows through the cooling gas supply pipes 19, 19 'into the chamber 29, 29' defined by the cylindrical element 23, 23 'and the sealing member 27,27'. From there,

  the gas is sent on the load 12 through the nozzles 21,21 '.

  The cooling gas flows through this charge and leaves the heating chamber 2 laterally through the chamber opening 9, 9 '. It is also possible to provide for this additional opening in the heating chamber 2. The cooling of the cooling gas takes place inside the heat exchanger 15, it leaves in the central part to be sucked back by the central part

  to be sucked in again by the suction pipe of the ventilator

16.

  During the quenching and cooling operation of the charge 12, the nozzles are pivotally driven to direct the cooling gas uniformly over the entire load 12. For this purpose, the cylindrical member 23, 23 ' performs a continuous movement in one direction and the other around the pivot axis 24,24 '. The treatment takes place completely

  automatic and we obtain a very fast and extremely

  uniformly uniform. The pivoting speed of the nozzles 21, 21 'can be reduced in the area of the end positions, so that during the pivoting movement, all the parts of the load

are also scanned.

  FIGS. 5a to 5g show diagrammatically

  arrangements of nozzle systems with types of construction

  different ovens. Figures 5a to 5d show horizontal construction furnaces. In the case of FIG. 5a, the nozzles are arranged at the top and bottom (embodiment shown in Figures 1 to 4). In the cases of FIG. 5b, the nozzles are arranged on the left and on the right and, in the case of FIG.

  nozzles are arranged at the top and bottom as well as left and right.

  For long furnaces (Fig. 5d), any number of nozzle systems can be arranged one behind the other. Figures 5e to 5g represent vertical furnaces. In the case of FIG. 5e, the nozzles are arranged on the left and on the right, and in

  the case of FIG. 5f, around the oven. Fig.5g represents a

  position of the nozzles in several stages.

11.

Claims (11)

  1) Industrial oven, especially vacuum chamber furnace   unique, for the heat treatment of metal parts,   both a heating chamber (2) disposed in a furnace chamber (1) and receiving a load (12), which chamber can be heated by heating elements (14) and having at least one closing chamber opening (9,9 ') for the passage of a gas   this gas can be put into circulation   to a heat exchanger using a fan (16), a   pivoting distributor device moved in one direction and in the   during the cooling operation being mounted, for controlling the flow of cooling gas flowing through at least one cooling gas duct (19, 19 '), in the zone   the chamber opening provided for the entry of the cooling gas   characterized in that nozzles (21,21 ') are provided   as a distributing device, the cooling gas is   flowing through these nozzles before reaching the load (12).   2) Industrial furnace according to claim 1, characterized   characterized in that the nozzles (21,21 ') are mounted immediately   before the chamber opening (9,9 ').   3) industrial furnace according to one of claims 1 and   2, characterized in that the nozzles (21, 21 ') are arranged with a cylindrical shape.   4) Industrial furnace according to claim 3, characterized   in that all the nozzles (21,21 ') have the same dia-   metre. Industrial furnace according to any one of Claims 1 to 4, characterized in that the pivot axis (24,24 ') of the nozzles (21,21') is arranged parallel to the section profile of the opening of chamber (9,9 ') and passing through the center of this profile, the nozzles (21,21') being arranged parallel to the pivot axis (24,24 ') along at least one line and symmetrically relative to to the mediator (M) of the section profile of the opening of room (9,9 '). 12.   6) Industrial furnace according to claim 5, characterized   in that the longitudinal axes (L) of the nozzles (21, 21 ')   run at a point (P) located upstream on the mediator (M) of the   section profile of the chamber opening (9,9 ').   7) An industrial furnace according to any one of claims 1 to 6, characterized in that the nozzles (21, 21 ') are   equipped with throttling devices (28,28 ').   8) Industrial furnace according to any one of the   1 to 7, characterized in that the nozzles (21, 21 ') are   placed in the casing (22,22 ') of a cylindrical element (23,23') whose axis coincides with the pivot axis (24,24 ') and whose external or internal lateral surface (26, 26 ') is sealingly applied during pivoting on a sealing element (27,   27 ') arranged parallel to the cylindrical element (23, 23'), the   the sealing element (27,27 ') closing, also sealingly, the end of the cooling gas supply pipe   (19,19 ') opening into the furnace chamber (1).   9) Industrial furnace according to any one of the   1 to 8, characterized in that the speed of rotation of the   nozzles (21,21 ') is reduced in the area of the end positions.    Industrial furnace according to any one of the   1 to 9, characterized in that the diameter of the nozzles (21,21 ') is at least equal to 1/10 of the distance between the nozzles   (21,21 ') and the point of incidence on the load (12).   11) Industrial furnace according to any one of the   1 to 10, characterized in that the faces of the heating chamber (2) opposite one another, in particular the bottom and the cover, are provided with similar corresponding openings.   (9,9 ') and nozzles (21,21') for the supply of the cooling gas   in the heating chamber (2),   12) Industrial furnace according to claim 11, characterized   in that the cooling gas supply pipes 13.   (19,19 ') to the nozzles (21,21') are equipped with butterflies of   (20,20 ') regulating the flow rate independently of one the other.   13) Industrial furnace according to any one of the   1 to 12, characterized in that a flow regulator   volume (18) is arranged before the fan (16) to   the cooling rate of the cooling gas sent to the nozzles (21,21 ').